JPH06506788A - Light sources, photodetectors, and devices using them - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Light sources, photodetectors, and devices using them field of invention The present invention allows the field of view of the photodetector and the illumination area of the light source to be in any plane on which the target is placed. An assembly of scanners or imaging devices that are coplanar and coextensive Regarding.

technology background In conventional mark sensing and mapping equipment, the light source and photodetector are separated; have optical paths that are not entirely congruent in space. Such devices provide important optical patterns. Provide an illumination area that includes the (meaning area) larger. The photodetector detects light entering the photodetector from the sensitive area. In particular, generate a responsive signal.

When the illuminated area is larger than the sensitive area, inset illumination is said to be present.

In this environment, it is difficult to accurately determine the information content of the scanned indicia or the interference. The process is detailed below.

FIG. 3 shows the illumination area 124 on the target object 123 with LED l 21 and LED 121. 1 shows a typical prior art device for illumination. The sensitivity area 122 is the illumination area 1 24 and are all contained within the illumination area 124. The sensitivity area 122 is, for example, is seen by a photodetector 127 through an optical device 125 consisting of a lens; 27 sends a signal to amplifier 129 in response to the detected light.

Mark detectors are typically barcode scanners or barcode readers. The output of the detector can be coupled to a decoding circuit. Expansion In barcode symbols on substrates including diffuse and laminated effects There are a number of known optical It has a scientific effect.

The diffusion effect can be understood with reference to FIGS. 4a and 4b. The diffusion effect is beam 1 26, i.e. outside the sensitive area 122 of the photodetector. It is generated from incident light. Beam 126 enters the substrate 138 on which the pattern is placed. irradiated and then diffused into the sensitive region within the substrate. The part of the diffused light is therefore The diffused light is transmitted to a photodetector via a sensitive region 122 that contributes to the received signal level. Returned at the end. In scanning applications such as barcode scanning, other diffusion effects result. In this application, the sensitive region is defined by bright (white) spaced regions. The signal is transmitted across the black bar that separates the signal.

These intervals are referred to here as white intervals, but are highly counterintuitive to those skilled in the art. It will be understood that the radioactive area is indicated. When the sensitivity area 122 approaches the black bar 139, As the black bar 139 increases, the white spacing of similar dimensions increases, as shown in Figure 4b. or absorb more light than it absorbs. Some light 128 is absorbed, so the sensitivity The degree of utilization that is spread close to the degree area is small. Therefore, the diffusion effect is either bar or sensitivity It changes quantitatively when it is close to the area than when it is not. This means barcode symbol 13 Analog waves generated by barcode scanning using inset illumination scanned by 2. The shape 130 may be seen with reference to FIG. Corresponding to the interference part with the white interval. The corresponding maximum value 135 or the minimum value signal 137 corresponds to a round, wide black bar. It is obvious that it is extremely sharp. Furthermore, between the narrow black bars 134 The peak value 136 corresponding to the narrow white interval is the width between the wide black bars 137. The amplification decreases in proportion to the maximum value 135 corresponding to the wide white interval 135 of . child The situation is predicted by the above discussion of diffusion effects. This narrow black/<one) reading When resolution cannot be achieved due to the modulation transfer function of the optical acquisition device, the pattern is divided into maximum and minimum values. It was symmetrical about When described in conjunction with diffusion effects or barcode scanning, Diffusion effects also affect non-traveling readers of optical patterns. In summary, diffusion While the effect does not affect the black level, it is clearly visible in the vicinity of the black no. There is a tendency to reduce the white level.

Other unwanted inset lighting effects in certain video applications such as barcode scanning are There is a lamination effect, also known as the Ohnolay effect. practical bar Code symbols often have a protective top laminate. The lamination effect is a sensitive region. is entirely reflected internally at the interface between the top laminate and the air above the area. Caused by light diffused from outside the sensitive area. Laminated with reference to Figure 6 Illustrating the effect of During the lamination process, laminate 141 and barcode expel the air between No. 142 and pour the adhesive onto the No. 140 code symbol board 140. . As a result, laminate +41! (- coat symbol +42 is familiar and contacts, Basically, the refractive index is matched. Laminated barcode substrate or lighting with diffusion effect rays such as rays 226a and 226b that sink outside the sensitive region 122. Bright incident light is diffused from the top surface of layer 142 into top laminate 141. , the surface 22 at an angle 144 that exceeds the critical angle for total internal reflection. 7. Such light rays 226a, 226b collectively cover the sensitivity region 1. reflected internally to 22. This portion of light is then directed back toward the top laminate 141. , diffuses through it, and finally reaches a photodetector that contributes to the received signal level. Ru.

When passing through a sensitive area or barcode symbol, as in the case of diffusion effects, the incident Some of the light is absorbed by the black 1<- adjacent to the sensitive area, thereby causing the white Decrease the signal level for long intervals. The size of the lamination effect depends on the thickness of the laminate , barcode symbol dimensions, bar and spacing reflectivity, nominal diffusion length in the substrate, and and reflection refractive index. While lamination effects are sometimes difficult to quantify , the area of this effect can be very large. The effect of lamination and diffusion is It usually impairs the performance of scanners, other forms of mark sensor detectors and video detection equipment. It is known for morphing.

When a small illumination source is used with a large sensitivity area of the so-called inset illumination sensitivity, It will be understood that similar arguments can be made if Generates a beam of light from a light source The beams of light are directed from the target toward the photodetector, and the beams of light are focused and shared. A number of methods have been used in the prior art to secure common operating areas. of light source The image and the defined sensitivity region are usually not congruent to a relatively deep field of view. these The reason is that all of these devices operate throughout all or most of the depth of field of view. This is because it is sensitive to deteriorating the diffusion effect and lamination effect.

For example, in U.S. Pat. No. 4,346,292 to Routt Jr. et al. An optical scanner is disclosed in which a source and reflected light beam are coaxially aligned toward a target. has been done. In this device, the sensitivity range is the field of view of only the illumination in the immediate vicinity of the focal plane and the actual field of view. Qualitatively congruent, the device provides a deep field of view without inset illumination of the target. cannot be achieved until.

U.S. Pat. No. 4,675.531 by C1erk et al. discloses that a scanner with a beam of . This beam, while having the same optical axis, has a sensitive region except at the focal plane. It is not possible to define a light source image that is congruent to the area. This device has a deep focus that requires no inset lighting. Not suitable for applications requiring points.

The device in U.S. Pat. No. 4,816,659 by Bianco et al. illuminated by a code symbol or lamp and received by a reflected beam or light-sensitive beam has been disclosed. This illumination and optical axis detection are coaxial in the plane of the A-code symbol. It doesn't match.

Summary of the invention Therefore, the first object of the invention is to create a mark that is insensitive to lamination and diffusion effects. An object of the present invention is to provide a device for detecting a sensing indicia.

Another object of the invention is that the image of the light source and the sensitive region of the light sensitive short term extend to the operating depth of the field of view. Detects mark-sensing indicia that are substantially coaxial, coplanar, and spread out in the same space. The objective is to provide an improved device for

Another object of the invention is to provide an improved barcode that is insensitive to lamination and diffusion effects. The goal is to produce a digital scanner.

These and other objects of the invention are directed to a barcode reader, such as a This can be accomplished by an optical assembly that can be housed within the mark-sensing detector.

The light source focuses the light onto a reflective target containing the barcode symbol to be scanned. A beam splitter that diverts part of a beam of light to another ).

The reflected beam is returned through an optical device and a beam splitter to A portion of the mu is conveyed to the photosensitive short word. In this way, the light-sensitive short circuit is removed from the mark-sensitive detector. The optical path to the word is separated twice by a beam splitter. Optical device illuminates the area defines a sensitivity region such that the beam of light passing through the optical device and the target mass has an equal optical It is constructed so that it is congruent with the axis and the divergence angle. Sensitive area emitted onto the illuminated area By properly specifying the axis of rotation of the image returned from the field onto the photodetector, the The image is substantially coplanar with the sensitive area at the operating depth of the field of view with the stray object. The rotation axes of the illumination area and sensitivity area are precisely aligned so that they are spread out in the same space. . The sensitive region therefore extends in any plane up to the depth of field of the optical device. and is congruent with the lighting area.

A viewing aperture is placed on the light source and the light-sensitive aperture to define the field of view and dimensions of the illuminated area. can be done. When this is achieved, the image of the aperture in the field of view of the light source is the sensitivity region The light that is emitted precisely above and returns to the sensitive area is the same as the visual aperture of the light sensitive short term. Expands in space and focuses.

Brief description of the drawing For a better understanding of these and other objects of the present invention, the attached drawings should be considered. The present invention will now be described in detail with reference to the following.

FIG. 1 is a schematic diagram showing an assembly according to the invention shown in the application of a barcode reader. and FIG. 2 is a side view of the device shown in FIG. 1, and FIG. 3 is a model of an optical reading device according to the prior art. 4a, 4b, and 5 are explanatory diagrams of the diffusion effect, and FIG. FIG. 7 is an explanatory diagram of the Neto effect, and FIG. 7 is a model diagram showing another embodiment of the present invention.

Detailed description of the invention In FIG. 1, an optical assembly according to the present invention is shown and described generally at 1°. . Although not illustrated for clarity, the assembly IO is the barcode scanner's Usually mounted within a housing. The housing allows the passage of light in the desired direction Raise a bad boat.

The function of the housing for the assembly IO is to block unwanted light from the light sensitive short term 24. It is to cut it off. In other applications, the invention can be used to Practice with appropriate measures, e.g. shielding, partially closed canopy You can do it. The light source 26 has a cross-sectional area and configuration defined by the field of view diaphragm 20 of the light source. In a preferred embodiment, a beam of light 36 is emitted. Light source 26 is preferably LED or laser, but incandescent lamp, arc lamp, or any suitable light source But that's fine. The image of the aperture 20 of the light source field emitted onto the target object 12 is not circular; Therefore, the diaphragm 20 of the light source field of view is such that the illumination area is rotated with the minimum barcode symbol element 13. Properly aligned around an axis of rotation such that the axes are aligned. Instead, the optical device It may be configured such that the rotation axes can be aligned. The aperture of the light source field of view is 20. It is preferably circular, but other field-of-view designs can also be used.

The beam of light 36 typically has a section positioned at a 45 degree angle to the beam of light 36. Finally, beam splitter 15, which is a mirror set splitter covered with silver, is struck.

Other angles may also be used to accommodate special applications. Part of beam 36 is continuously extinguished beyond the beam splitter 15, and the remainder of the beam is It is reflected by the liter 15 and directed toward the lens 14 at a divergence angle 18 .

Lens 14 focuses the image of the field of view aperture 20 of the light source on barcode symbol 12. Any suitable lens or lens arrangement shown in FIG. The gap 28 is Provided to control lens aberrations. Area 21 is the useful movement of the field of view of the instrument. The depth can be defined and varied by proper design of the gap-lens combination, which is known in the art. can be changed. A beam of light passes through lens 14 and hits area 1 of the barcode symbol. 7, the field of view of the light source formed by the lens 14 above the aperture 20 of the field of view of the light source. The width dimension of the light image of the field aperture 20 is approximately the width 13 of the smallest element of the barcode symbol. is the lateral dimension of

The reflected light from area 17 is captured by lens 14 and sent to beam splitter 15. be returned. A portion of the light passes through the beam splitter and passes through the barcode symbol area 17. is projected by the lens 14 onto the aperture 22 of the light-sensitive short field of view. Area 17? The energy of the light reflected from the light is therefore the last to be received by the light-sensitive short term 24; generates a signal in response to the reception of light. The signal generated by sensor 24 is a normal signal. signal processing circuit. As defined by the visual aperture 22 of the light-sensitive short term, A beam of light 38 extending from the light sensor 24 to the beam splitter 15 has an angle of 18 Develop a divergence angle 16 equal to .

Field stops 20 and 22 are equal in size and configuration. these are , equidistant from the beam splitter and close to the light source and light-sensitive short term, respectively, and the area The images of these lights at 21 are spread on the same axis, on the same plane, and in the same space. Like, directed. The cone-shaped beam of light defined by the field diaphragm is As shown in FIG. are congruent in three dimensions.

The light sensor 24 is a commonly used one, such as a light emitting diode, an avalanche ( avalanche) light emitting diode, photomultiplier, light emitting transistor, or An optical FET may also be used.

The device can be operated without viewing apertures 20 and 22, and the light in area 21 The focus of the image of the photosensitive area of the sensor 24 and the light source 26 can be brought into direct focus.

However, the field aperture is limited by the strain from the filament image and the structural details of the photosensitive short term. Useful for avoiding conflicts. The viewing apertures 20 and 22 are connected to a light source 26 and a light-sensitive aperture 24. can be provided as integrated parts of each. Light-sensitive short words are, of course, It responds to unfocused light passing through the field aperture 22.

The positions of the light source 26 and the light sensitive wire 24 can be replaced without affecting the functionality of the device. That is something I am grateful for.

FIG. 7 shows another embodiment of the invention, in which reference numerals for like elements with respect to FIG. It is shown by adding 400 to the reference number of the element.

The light source 426 is preferably provided through an aperture 420 of the source field of view that defines the cross-sectional area and structure. and emits a beam of light 436.

The beam of light 436 is now directed through the second lens 414 at a divergence angle 418. I will be forgotten. Lens aberrations are reduced by lens 514 as well as gap 528.

The beam of light passing through the lens 514 is finally aligned with the optical axis of the beam of incident light 436. and hit the beam splitter 415 arranged at 45 degrees. Other angles also have special application Can be used together. Typically a 50% beam splitter is used, but if desired It can be changed. A portion of the beam 436 crosses the beam bulge and ivy 415. The rest of the beam is reflected by the beam drop and ivy 415. and is directed at a focusing target 412 at an angle 419.

When the beam of light passing through lens 514 strikes area 417 of the barcode symbol, The width dimension of the optical image of the field of view diaphragm 420 of the light source formed by the lens 514 is \ - is the approximate lateral dimension of the code symbol minimum element width 413.

The light reflected from the barcode symbol area 417 is reflected onto the beam subli vine 415. incident. A portion of the light passes through the beam holder and the second lens 414. The light-sensitive short word is then transmitted to the visual aperture 422 of the light-sensitive short word, and finally generates a response signal. The light is received by 424. This signal is transmitted to a signal processing circuit. lens 414 The gap 428 coupled to reduces lens aberrations.

In this example, the lens-gap combinations 414 and 428.514 and 528 The images of field apertures 420 and 422 are located at barcode symbol 412. Provided to be substantially coaxial and coplanar at the operating depth of the field of view. Len Although the beam splitter 415 and the light-sensitive short beam 424 do not necessarily have to be the same, The light source 426 and the beam splitter 41 are arranged so that the optical path has a different length from the optical path between them. Geometrically constrained and accommodated within the scanner housing requiring an optical path between 5 and 5 It can be designed as such.

Field apertures 420 and 422 are geometrically the same in shape, but are equal in size. There's no need to. These are placed in close proximity to the light source and the light sensitive word, respectively. of sight The cone-shaped beam of light defined by the aperture is substantially It will be congruent in three dimensions.

Field apertures 422 and 420 can be integrated with light sensor 424 and light source 426.

This means that the positions of the light source 426 and the light sensitive shortcut 424 can be interchanged without affecting the functionality of the device. That is something I am grateful for. The optical path of the bent light also lies in the operating region described above. may be used without departing from the spirit of the invention, as long as the desired congruence is maintained. cormorant.

While the present invention has been described with respect to the structure disclosed herein, the present invention has been described in detail above. Without limitation, this application may be accomplished within the scope of the following claims. It includes any modifications and changes.

Continuation of front page (72) Inventor Kuchi Ngakure, Andrew, Jr. United States of America, New 21 Leitch Avenue, York 13152 Skaneateles

Claims (11)

[Claims] 1. a light source means for emitting a beam of light illuminating the target and a sensitive area on the target; light sensor means for generating a signal in response to light energy received from the light sensor; fixing the sensitive area on the target and generating an image of the light source on the target; an optical means in the optical path of said beam of light, said sensitivity in said optical means; The area and said image are beams of light that are substantially congruent throughout the effective operating depth of the field of view. The sensitive region and the image can be further rotated to align their axes. can be done, Thereby, the sensitive region and the image are substantially coextensive on the target. and means for blocking unnecessary light from the light sensor means. An optical assembly for use in detecting an indicium, comprising: 2. The light source means dimensions the cross-sectional area and outer shape of the emitted beam of light. further comprising a first field diaphragm means, wherein the light sensor means is connected to the light image forming means. a step of dimensioning the cross-sectional area and structure of the beam of light directed towards said photodetector means; Further equipped with a two-field aperture means, The optical imaging means is substantially coplanar and coplanar throughout the operational depth. forming an image of the first field diaphragm and the second field diaphragm spreading in space; An assembly according to claim 1, wherein the assembly is configured. 3. The assembly according to claim 2, wherein the first field stop means is integrated with the light source means. Mburi. 4. 3. The assembly according to claim 2, wherein the second field stop means is integrated with the photodetector. Mburi. 5. The optical image forming means includes: placed in the optical path of the emitted beam of light and the light reflected from the target object; directing a portion of the reflected light toward the light sensor means and directing a portion of the emitted beam of light; beam splitter means for directing the beam toward the target; lens means for generating a light image; The assembly of claim 1, comprising: 6. gap means cooperating with said lens means to reduce aberrations in said lens means; 6. The assembly of claim 5, further comprising: 7. housing and a light source means for emitting a beam of light illuminating the target and receiving from a sensitive region on the target; a light sensor hand cooperating with said housing that generates a signal in response to light energy emitted from the housing; fixing the sensitive area on the target and creating an image of the light source on the target; an optical means disposed in the optical path of the beam of light, the front part of the optical means being The recording sensitivity region and the image are substantially congruent throughout the useful working depth of field. defined by the light beam, The sensitivity region and the image are further aligned with the axis of rotation, thereby increasing the sensitivity. The region and the image are optically configured to be substantially coextensive on the target object. A barcode scanning device comprising: means. 8. The light source means are arranged adjacently in the optical path of the emitted light beam. further comprising a first field diaphragm, the light sensor means being in front of the light imaging means; In the path of the beam of light directed to the recording image forming means, a second Additionally equipped with a 2-field aperture, The optical imaging means is substantially coplanar and substantially coplanar throughout the effective working depth. forming images of the aperture means of the first field of view and the aperture means of the second field of view that are spread in the same space; 8. A barcode scanning device according to claim 7, configured to. 9. Define the sensitivity region containing the indicia read against the photodetector at the depth of view. Arrived, Directing light from a light source onto the sensitive area and extending the sensitive area all the way to the depth of the field of view. an image of the light source at the depth of the field of view that extends substantially in the same plane and in the same space within the area; and generating a signal at the photodetector in response to reflected light from the sensitive region. Ru Read the indicia on the board located within the effective operating depth of the field of view with each step. How to take it. 10. sizing light from the light source directed onto the sensitive region; 10. The method according to claim 9, further comprising: 11. 10. The method of claim 9, further comprising sizing the reflected light.